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| United States Patent |
5,637,784
|
|
Chu
, et al.
|
June 10, 1997
|
Hydrocarbon distillate fuels containing novel additive
Abstract
A hydrocarbon oligomer and a process for its production is disclosed that
is useful as a pour point depressant and as a combination pour point
depressant and viscosity index improver for mineral oil or synthetic oil.
The oligomer is also useful in modifying wax crystal formation at low
temperature when added to distillate fuels. The oligomer is a near linear
copolymer of a mixture of ethylene and C.sub.3 -C.sub.28 1-alkenes, or
only 1-alkenes, wherein a large proportion of the pendant alkyl groups of
the recurring 1-alkene monomer units contain between 14 and 22 carbon
atoms. The oligomer is produced by polymerization of mixed 1-alkenes with
reduced chromium oxide catalyst on silica support.
| Inventors:
|
Chu; Alice S. (Spotswood, NJ);
Jackson; Andrew (Pennington, NJ);
Wu; Margaret M. (Skillman, NJ)
|
| Assignee:
|
Mobil Oil Corporation (Fairfax, VA)
|
| Appl. No.:
|
536724 |
| Filed:
|
September 28, 1995 |
| Current U.S. Class: |
585/14; 585/530 |
| Intern'l Class: |
C10L 001/16 |
| Field of Search: |
585/14,530
|
References Cited
U.S. Patent Documents
| 4827023 | May., 1989 | Hsu | 560/204.
|
| 4827064 | May., 1989 | Wu | 585/10.
|
| 5146021 | Sep., 1992 | Jackson et al. | 585/10.
|
| 5157177 | Oct., 1992 | Pelrine et al. | 585/530.
|
| 5243114 | Sep., 1993 | Johnson et al. | 585/530.
|
| 5264642 | Nov., 1993 | Wu | 585/530.
|
Primary Examiner: Howard; Jacqueline V.
Attorney, Agent or Firm: Keen; Malcolm D.
Parent Case Text
This is a division of application Ser. No. 08/178,152, filed on Jan. 6,
1994, now U.S. Pat. No. 5,488,191.
Claims
What is claimed is:
1. A process for the production of a hydrocarbon lubricant additive
suitable as a pour point depressant and viscosity index improver
comprising contacting a mixture of olefin comonomers selected from the
group consisting of ethylene and C.sub.3 -C.sub.28 1-alkenes with a
reduced valence state Group VIB metal catalyst on a porous support under
copolymerization conditions, said mixture comprising a bimodal
distribution of 1-alkenes having a first maximum between C.sub.3 and
C.sub.14 1-alkenes and a second maximum between C.sub.14 and C.sub.26
1-alkenes; and separating a copolymer comprising said additive.
2. The process of claim 1 wherein said mixture is selected from C.sub.6
-C.sub.24 1-alkenes.
3. The process of claim 1 wherein said catalyst comprises reduced CrO.sub.3
and said support comprises silica having a pore size of at least 40
Angstroms.
4. The process of claim 1 wherein said copolymerization conditions comprise
temperature between 25.degree. C. and 150.degree. C.
5. The process of claim 4 wherein said temperature is between 25.degree. C.
and 95.degree. C.
6. A liquid fuel mixture comprising diesel fuel and the copolymer a
near-linear liquid hydrocarbon copolymer which is effective to inhibit the
low temperature formation of wax particles in liquid hydrocarbon
lubricants and fuels, said copolymer comprising poly(1-alkene) and
containing between 300 and 4500 carbon atoms wherein said copolymer
residue contains a bimodal distribution of said 1-alkenes comprising a
first maximum between C.sub.3 and C.sub.14 1-alkenes and a second maximum
between C.sub.14 and C.sub.26 1-alkenes, and wherein recurring monomeric
units of said copolymer comprise a mixture olefins selected from ethylene
and C.sub.3 -C.sub.28 1 -alkenes where at least 10 weight percent of the
pendant chains of said copolymer contain between 12 and 22 carbon atoms.
7. A hydrocarbon fuel composition containing a hydrocarbon fuel additive
suitable as a pour point depressant, said additive comprising the
copolymer residue of a mixture of 1-alkene comonomers selected from
C.sub.3 -C.sub.28 1-alkenes, wherein said copolymer contains at least 10
weight percent of recurring monomeric units of C.sub.4 -C.sub.24
1-alkenes; has a number average molecular weight between 5,000 and 60,000;
a molecular weight distribution between 1 and 10 and a bimodal
distribution of said 1-alkenes comprising a first maximum between C.sub.3
and C.sub.14 1-alkenes and a second maximum between C.sub.14 and C.sub.26
1-alkenes.
8. The composition of claim 2 wherein said coploymer residue contains a
bimodal distribution of said 1-alkenes comprising a first maximum between
C.sub.3 and C.sub.14 1-alkenes and a second maximum between C.sub.14 and
C.sub.26 1-alkenes.
9. The composition of claim 7 wherein said mixture of 1-alkenes comprises a
bimodal mixture of C.sub.6 -C.sub.24 1-alkenes.
10. The composition of claim 7 comprising the copolymer of 1-decene or
1-hexane and 1-octadecene.
11. The composition of claim 10 wherein the mole ratio of 1-decene or
I-hexane to 1-octadecene is about 3 to 2.
12. The composition of claim 7 in which the copolymer residue comprises a
near-linear liquid hydrocarbon copolymer effective to inhibit the low
temperature formation of wax particles in the fuels, said copolymer
comprising poly(1-alkene) and containing between 300 and 4500 carbon
atoms, wherein recurring monomeric units of said copolymer comprise a
mixture olefins selected from ethylene and C.sub.3 -C.sub.28 1-alkenes
where at least 10 weight percent of the pendant chains of said copolymer
contain between 12 and 22 carbon atoms.
13. The composition of claim 12 wherein said recurring units comprise a
mixture of C.sub.6 -C.sub.24 1-alkenes.
14. The composition of claim 12 comprising the copolymer of 1-decene or
1-hexane and 1-octadecene.
15. The composition of claim 12 wherein said fuel comprises diesel fuel.
16. The composition of claim 12 containing between 0.01 and 1.0 weight
percent of said pour point depressant.
Description
This invention relates to novel additives for hydrocarbon lubricants and
distillate fuels and to the process for their production. The invention
particularly relates to novel hydrocarbon additives useful as pour point
depressants and additives which show combined pour point depressant and
viscosity index improving properties for hydrocarbon lubricants and
inhibitors of waxy particle formation in diesel fuel at low temperatures.
The novel additives are produced by reduced chromium oxide catalyzed
polymerization of mixed 1-alkenes rich in C.sub.18 + 1-alkenes.
BACKGROUND OF THE INVENTION
The formulation of synthetic or mineral oil based lubricants typically
includes an additive package incorporating a variety of chemicals to
improve or protect lubricant properties in application specific
situations, particularly internal combustion engine and machinery
applications. The more commonly used additives include oxidation
inhibitors, rust inhibitors, antiwear agents, pour point depressants,
detergent-dispersants, viscosity index (VI) improvers, foam inhibitors and
the like. This aspect of the lubricant arts is specifically described in
Kirk-Othmer "Encyclopedia of Chemical Technology", 3rd edition, Vol. 14,
pp 477-526, incorporated herein by reference. The inclusion of additives
in hydrocarbon lubricants provides a continuing challenge to workers in
the field to develop improved additives of increased compatibility with
the lubricant. Superior additives, while contributing their inherent
attribute to the formulation, must do so while maintaining or improving
upon the composite thermal and oxidative stability of the lubricant
formulation.
The low temperature flow characteristic of hydrocarbon lubricants are
typically improved by adding pour point depressants (PPD) to the
formulation. At low temperatures, these additives modify the shape and
size of the precipitating waxy hydrocarbon crystal to slow agglomeration
and lower the effective pour point temperature of the lubricant
formulation. Currently, preferred pour point depressants include
polymethacrylates and ethylene-vinyl ester polymers. However, hydrocarbon
based pour point depressants are known.
Polyalphaolefin (PAO) pour point depressants are described by Chong-Xiang
Xiong in "The Structure and Activity of Polyalphaolefins as Pour Point
Depressants", published in the Journal of the Society of Tribologists and
Lubrication Engineers, March, 1993, pp 196-200. The PPD is prepared by
polymerization of slack wax-derived C.sub.7 -C.sub.20 alphaolefins using
Ziegler-Natta catalyst. It is reported that PAO pour point depressant
activity depends on average side chain length and on the distribution of
the side chain length. Base oil characteristics influence the
effectiveness of specific PAO pour point depressants.
It is also known that the low temperature flow properties of waxy
distillate fuels can be improved by employing wax crystal modifiers as
additives to fuels in a manner functionally similar to waxy lube PPD. The
use of such additives to distillate fuels avoids the more costly step of
deep dewaxing of the distillate feedstock.
One class of lubricants of particular interest in the present invention is
synthetic lubricants obtained by the oligomerization of olefins,
particularly C.sub.3 -C.sub.20 alpha olefins. Catalytic oligomerization of
olefins has been studied extensively. Known olefin oligomerization
catalysts include the Ziegler-Natta type catalysts and promoted catalysts
such as BF.sub.3 or AlCl.sub.3 catalysts. U.S. Pat. No. 4,613,712 for
example, teaches the preparation of isotactic alpha-olefins in the
presence of a Ziegler type catalyst. Other coordination catalysts,
especially chromium on a silica support, are described in the art.
Recently, novel lubricant compositions (referred to herein as HVI-PAO and
the HVI-PAO process) comprising polyalphaolefins and methods for their
preparation employing as catalyst reduced chromium on a silica support
have been disclosed in U.S. Pat Nos. 4,827,064 and 4,827,023, incorporated
herein by reference in their entirety. The process comprises contacting
C.sub.6 -C.sub.20 1-alkene feedstock with reduced valence state chromium
oxide catalyst on porous silica support under oligomerizing conditions in
an oligomerization zone whereby high viscosity, high VI liquid hydrocarbon
lubricant is produced having low methyl to methylene branch ratios of less
than 0.19 and pour point below -15.degree. C. The process is distinctive
in that little isomerization of the olefinic bond occurs compared to known
oligomerization methods to produce polyalphaolefins using Lewis acid
catalyst.
U.S. Pat. No. 5,146,021 to Jackson, et al. discloses lube compositions of
HVI-PAO with mineral oil and polyolefins wherein oligomers from mixtures
of C.sub.6 -C.sub.20 alphaolefins are employed to provide high VI
additives and shear stability. However, the patent does not claim or
disclose the use of mixtures containing a high proportion of C.sub.18 +
alpha olefins to produce improved pour point depressants. U.S. Pat. No.
5,157,177 to Pelrine et al. discloses the oligomerization process relevant
to the preparation of the foregoing HVI-PAO compositions. The compositions
and process disclosed in these patents encompass polymer compositions that
contain non-waxy components. The polymers are useful as lubricants with
low pour point.
The object of the present invention is the production of novel lubricant
additive hydrocarbon compositions that are highly effective as pour point
depressants and/or combined pour point depressant and viscosity index
improver (VII) produced by catalytic oligomerization of 1-alkenes.
Another object of the present invention is to provide an improved process
for the production of pour point depressants by oligomerization of
1-alkenes using silica supported reduced chromium oxide catalyst.
Yet another object of the invention is to provide a pure hydrocarbon
additive for distillate fuels that is effective in modifying wax crystal
growth at low temperatures.
SUMMARY OF THE INVENTION
Hydrocarbon oligomers, and a process for their production, have been
discovered that show superior properties as pour point depressants for
mineral oil or synthetic oil. The oligomesr are also useful in modifying
wax crystal formation at low temperature when added to distillate fuels.
The oligomer is a near linear copolymer of a mixture of ethylene and
C.sub.3 -C.sub.22 1-alkenes, or only 1-alkenes, wherein a large proportion
of the pendant alkyl groups of the recurring 1-alkene monomer units
contain between 12 and 22 carbon atoms, preferably between 14 and 18
carbon atoms. The linearity of the 1-alkene copolymer is distinguished by
the relatively small amount of isomerization that occurs during
copolymerization by the process disclosed in U.S. Pat Nos. 4,827,064 and
4,827,023 and evinced by a methyl to methylene branch ratio of less than
0.19 for oligomers formed from C.sub.6 + 1-alkenes.
The superior pour point depressant properties of the compositions of the
invention are preferably achieved by preparing oligomers from a feedstream
mixture of ethylene and C.sub.3 -C.sub.28 1-alkenes, or only C.sub.3
-C.sub.28 1-alkenes, wherein the distribution of carbon numbers is bimodal
instead of monomodal. Bimodal distribution in the present invention means
that carbon number distribution in the total feedstream is skewed in such
a manner as to exhibit two peaks, one peak of low carbon number and
another peak of high carbon number. The bimodal feedstream produces the
bimodal 1-alkene copolymers of the present invention comprising copolymers
having a first maximum of pendant carbon chains with between one and 12
carbon atoms and a second maximum of pendant carbon chains with between
twelve and twenty-four carbon atoms.
In comparison to pour point depressants known in the art, the novel
hydrocarbon oligomers of the invention show a dramatic capability to
reduce the low temperature pour point of mineral oils and synthetic oils
when mixed with such liquids in quantities of less than 1 weight percent.
When mixed with diesel fuels containing hydrocarbons that normally form
wax crystals at low temperature, the oligomers of the invention modify the
formation of wax crystals and minimize wax formation in the fuel.
As VI improvers, these novel hydrocarbon oligomers work as effectively as
the single olefin based HVI-PAO's disclosed in U.S. Pat. No. 5,146,021. In
addition, they add pour point depressant function to the VI improver. The
novel oligomers of the invention are cited herein as mixed alpha-olefin
HVI-PAO, or MHVI-PAO, to distinguish them over the HVI-PAO oligomers of
the prior art.
The products of the invention are prepared by oligomerizing olefins,
preferably a mixture of C.sub.6 -C.sub.24 1-alkenes containing at least 10
weight percent of C.sub.4 -C.sub.24 1-alkenes, preferably C.sub.16
-C.sub.20 1-alkenes, in contact with supported reduced valence state
chromium oxide catalyst.
More particularly, a hydrocarbon lubricant additive has been discovered
that is suitable as a pour point depressant. The additive comprises the
copolymer residue of a mixture of 1-alkene comonomers selected from the
group consisting of C.sub.3 -C.sub.28 1-alkenes. The copolymer contains at
least 10 weight percent of C.sub.14 -C.sub.24 1-alkenes, but preferably 20
weight percent. It also has a number average molecular weight between
5,000 and 60,000; and a molecular weight distribution between 1 and 10.
The product of the invention is a near-linear liquid hydrocarbon copolymer
useful in modifying the low temperature formation of wax particles in
liquid hydrocarbon lubricants and fuels. The copolymer comprises
poly(1-alkene) having a low methyl to methylene branch ratio and
containing between 300 and 4500 carbon atoms, wherein recurring monomeric
units of said copolymer comprise a mixture of ethylene and C.sub.3
-C.sub.28 1-alkene, or C.sub.3 -C.sub.28 1-alkenes, and at least 10 weight
percent of the pendant chains of said copolymer contain between 12 and 22
carbon atoms, most preferred pendant chains are C.sub.14 to C.sub.18.
The product of the invention is prepared by contacting a mixture of olefin
comonomers selected from the group consisting of ethylene and C.sub.3
-C.sub.28 1-alkenes with a reduced valence state Group VIB metal catalyst
on a porous support under copolymerization conditions. The mixture
contains at least 10 weight percent of C.sub.14 -C.sub.24 1-alkenes,
preferably C.sub.16 -C.sub.20 1-alkenes. The product of the
copolymerization is separated and a copolymer comprising the additive is
recovered.
DESCRIPTION OF THE FIGURES
FIG. 1 is a graphical representation comparing the feed composition of
HVI-PAO versus the novel MHVI-PAO oligomers of the invention.
FIG. 2 is a graphical representation of the feed composition of HVI-PAO of
the prior art.
FIG. 3 is a graphical representation of the feed composition of one
preferred embodiment of MHVI-PAO of the invention.
FIG. 4 is a graphical representation of the feed composition of another
preferred embodiment of MHVI-PAO of the invention.
FIG. 5 is a graphical representation of the feed composition of yet another
preferred embodiment of MHVI-PAO of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Olefins useful as feedstock in the present invention include ethylene and
C.sub.3 -C.sub.28 1-alkenes of odd and even carbon number. The preferred
olefins are 1-alkenes, i.e., alpha-olefins selected from the group
consisting of C.sub.6 -C.sub.24 1-alkenes. The preferred long chain
1-alkenes comprise C.sub.14 -C.sub.24 .alpha.-olefins. The most preferred
long chain 1-alkenes comprise C.sub.6 -C.sub.20 .alpha.-olefins.
A feature inherent to the novelty of the instant invention is that the
feedstock include a mixture of 1-alkenes and that the mixture of 1-alkenes
comprise at least 10 weight percent C.sub.16 -C.sub.24 1-alkenes. The
mixture may be a mixture of only two such 1-alkenes, for example, 1-hexene
and 1-octadecene, 1-decene and 1-eicosene, or it may be a mixture that
includes propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene,
1-nonene, 1-decene, and higher 1-alkenes up to and including C.sub.28
1-alkene. In any event, at least 10 weight percent, but preferably 20
weight percent, of the 1-alkenes of the mixture will be 1-alkenes
containing 16 to 24 carbon atoms.
The feedstock for the process of the invention can be acquired from a
variety of processes and process streams common to modern petroleum
refining operations. The products of slack wax cracking, ethylene growth
reaction and Fischer-Tropsch alpha olefin process are useful sources of
mixed 1-alkenes. These and other sources of feed-stock may contain alkanes
and internal olefins. As a result, the 1-alkene feedstream to the process
of the invention itself may contain these alkanes and internal olefins.
However, these are not reactive in the oligomerization reaction of the
invention.
The oligomerization reactions of the invention are catalyzed by supported
metal oxide catalysts, such as Cr compounds on silica or other supported
IUPAC Periodic Table Group VIB compounds as described in U.S. Pat.
4,827,064 to M. Wu. The catalyst most preferred is a lower valence Group
VIB metal oxide on an inert support. Preferred supports include silica,
alumina, titania, silica alumina, magnesia and the like. The support
material binds the metal oxide catalyst. These pourous supports may be in
powder form or in extrudate form. Those porous substrates having a pore
opening of at least 40 angstroms are preferred.
The support material usually has high surface area and large pore volumes
with average pore size of 40 to about 350 angstroms. The high surface area
are beneficial for supporting a large amount of highly dispersive, active
chromium metal centers and to give maximum efficiency of metal usage,
resulting in very high activity catalyst. The support should have large
average pore openings of at least 40 angstroms, with an average pore
opening of >60 to 300 angstroms preferred. For this catalyst to be used in
fixed bed or slurry reactor and to be recycled and regenerated many times,
a silica support with good physical strength is preferred to prevent
catalyst particle attrition or disintegration during handling or reaction.
The supported metal oxide catalysts are preferably prepared by impregnating
metal salts in water or organic solvents onto the support. Any suitable
organic solvent known to the art may be used, for example, ethanol,
methanol, or acetic acid. The solid catalyst precursor is then dried and
calcined at 200.degree. to 900.degree. C. by air or other
oxygen-containing gas. Thereafter the catalyst is reduced by any of
several various and well known reducing agents such as, for example, CO,
H.sub.2, NH.sub.3, H.sub.2 S, CS.sub.2, CH.sub.3 SCH.sub.3, CH.sub.3
SSCH.sub.3, metal alkyl containing compounds such as R.sub.3 Al, R.sub.3
B,R.sub.2 Mg, RLi, R.sub.2 Zn, where R is alkyl, alkoxy, aryl and the
like. Preferred are CO or H.sub.2, CO or H.sub.2 containing gas or metal
alkyl containing compounds.
Alternatively, the Group VIB metal may be applied to the substrate in
reduced form, such as CrII compounds. The catalyst can be used in a batch
type reactor or in a fixed bed, continuous-flow reactor.
In general the support material may be added to a solution of the metal
compounds, e.g., acetates or nitrates, etc., and the mixture is then mixed
and dried at room temperature. The dry solid gel is purged at successively
higher temperatures to about 600.degree. for a period of about 16 to 20
hours. Thereafter the catalyst is cooled down under an inert atmosphere to
a temperature of about 250.degree. to 450.degree. C. and a stream of pure
reducing agent is contacted therewith for a period when enough CO has
passed through to reduce the catalyst as indicated by a distinct color
change from bright orange to pale blue. Typically, the catalyst is treated
with an amount of CO equivalent to a two-fold stoichiometric excess to
reduce the catalyst to a lower valence CrII state. Finally the catalyst is
cooled down to room temperature and is ready for use.
Example 1 specifically illustrates the method for preparation of the
catalyst employed in the present invention and disclosed in U.S. Pat. No.
4,827,064.
EXAMPLE 1
Catalyst Preparation and Activation Procedure
1.9 grams of chromium (II) acetate (Cr.sub.2 (OCOCH.sub.3).sub.4 2H.sub.2
O)(5.58 mmole) (commercially obtained) is dissolved in 50 cc of hot acetic
acid. Then 50 grams of a silica gel of 8-12 mesh size, a surface area of
300 m.sup.2 /g, and a pore volume of 1 cc/g, also is added. Most of the
solution is absorbed by the silica gel. The final mixture is mixed for
half an hour on a rotavap at room temperature and dried in an open-dish at
room temperature. First, the dry solid (20 g) is purged with N.sub.2 at
250.degree. C. in a tube furnace. The furnace temperature is then raised
to 400.degree. C. for 2 hours. The temperature is then set at 600.degree.
C. with dry air purging for 16 hours. At this time the catalyst is cooled
down under N.sub.2 to a temperature of 300.degree. C. Then a stream of
pure CO (99.99% from Matheson) is introduced for one hour. Finally, the
catalyst is cooled down to room temperature under N.sub.2 and is ready for
use.
While providing oligomers having a very low branch ratio, the
oligomerization of 1-alkenes with reduced chromium oxide catalyst on
silica support also provides a highly uniform structural composition,
particularly when compared to conventional polyalphaolefins produced by
BF.sub.3, AlCl.sub.3 or Ziegler-type catalysis. HVI-PAO oligomers have
been shown to have a very uniform linear side chain branch and contain
regular head-to-tail connections. The oligomers are essentially linear. In
addition to the structures from the regular head-to-tail connections, the
backbone structures have some head-to-head connections.
It has been discovered that activated reduced chromium catalyst on
SiO.sub.2 support efficiently produces polymers with the right molecular
weight range and chemical composition to form useful additives from wide
mixtures of alphaolefins. The mixed olefin based HVI-PAO polymers show a
very large pour point depressant effect when blended with wax containing
lubricant basestocks. This result is evident while the mixed olefin based
polymers also are effective as viscosity index improvers (VII). The mixed
olefin based HVI-PAO produced from reduced chromium catalyst on SiO.sub.2
support can also minimize wax formation when blended with diesel fuel.
Thus, it can be used to improve the flow properties of waxy fuels at low
temperature. Since HVI-PAO polymers are pure hydrocarbons they will have
better thermal stability, oxidative stability and solubility in
hydrocarbon lubricants and distillate fuels then commercial pour point
depressants or wax crystallization modifiers. These commercial additives
are mostly polymethacrylates or ethylene-vinyl ester copolymers.
Examples of specific lubricant base stocks for which the polymers of the
invention are effective as pour point depressants are summarized as
follows and their physical properties are presented in Table 1:
LN142-100", solvent neutral mineral base stock, available from Mobil Oil
Corp. as product number 71326-3, produced by methyl ethyl ketone solvent
dewaxing;
LN321-150", solvent neutral mineral base stock, produced by catalytic
dewaxing;
HN339-700", heavy neutral mineral base stock, produced by catalytic
dewaxing;
BS345--bright stock mineral oil, produced by catalytic dewaxing;
WHI-A, WHI-B stocks--derived from slack wax. The wax is hydroisomerized at
high pressure, such as 1500-3000 psi over an amorphous catalyst or
zeolite.
PAO-1, a 2 cS synthetic hydrocarbon poly-alpha-olefin fluid available from
Mobil Chemical.
PAO-2, a 5.5 cS synthetic hydrocarbon poly-alpha-olefin fluid available
from Mobil Chemical.
TABLE 1
______________________________________
Base Stock Properties
Viscosity, cS Pour
Stock No.
Stock Type 100.degree. C.
40.degree. C.
VI Point .degree.C.
______________________________________
LN142 mineral, 4.19 21.23 97 -14
solvent dewax
LN321 mineral 4.61 24.1 106 -3
catalytic dewax
HN339 mineral 13.08 138.53
86 -12
catalytic dewax
BS345 mineral 30.2 460.62
94 4
catalytic dewax
WHI-A wax-isomerized,
5.35 26.1 144 -16
solvent dewax
WHI-B wax-isomerized,
5.14 24.16 148 -15
solvent dewax
______________________________________
As noted, the products of the invention are useful in modifying wax
formation in distillate fuels. Generally, distillate fuels include jet
fuels, diesel fuels and heating oils. The compositions of the present
invention are particularly useful in automotive and railroad diesel fuels.
The process and compositions of the present invention are described by
illustrating their preparation and properties in the following Examples
2-11. The Examples include the method for the preparation of the novel
polymers of the invention (Example 2) and the properties of blends of the
novel polymers with various lubricant basestock (Examples 3-10) and with
diesel fuel (Example 11). The catalyst used in the oligomerization of the
mixed 1-alkene monomers is prepared according to the method described in
Example 1. The results are shown in Table 2 for the preparation of the
copolymer of the invention and Table 3 shows the properties of blends
prepared from the copolymer with mineral oil and synthetic lubricants
(Examples 2-9).
EXAMPLE 2
Six grams of Cr/SiO.sub.2 catalyst prepared as described in Example 1 were
mixed with an alpha olefin mixture containing six to twenty carbon numbers
and the mixture was stirred at room temperature for twenty-four hours. The
alpha olefin mixture has a composition comparable to the alpha olefin
mixture produced from a single stage ethylene growth reaction and is
reported in Table 2. Gas chromatograph (GC) analysis of the polymer
solution produced from the oligomerization reaction of alphaolefins showed
that 70% to 90% of the alpha olefins were converted into polymers. The
slurry mixture was very thick and 400 cc of xylene was added to dilute and
quench the catalyst. The mixed olefin based HVI-PAO polymer was isolated
by filtration to remove the catalyst, followed by distillation at
160.degree. C. and 100 millitorr to remove solvent and any unreacted
olefins. As shown in Table 2, the polymer composition contained different
amounts of alphaolefins. All of the alphaolefins in the starting mixture
were converted into polymer. The residual olefins were internal or
branched olefins present in the starting mixture. This polymer had a
number average molecular weight of 18,200, weight average molecular weight
of 58,000 and molecular weight distribution of 3.19.
EXAMPLE 3
The sample prepared in Example 2 was blended with a light neutral
paraffinic mineral base stock, LN321, which was dewaxed using a catalytic
dewaxing process. The properties of the base stock and the blends are
summarized in Table 3. These data show that the blend containing 0.26
weight percent of the product of Example 2 has a pour point of -38.degree.
C. and cloud point of 3.0.degree. C., a 35.degree. C. pour point reduction
and 2.6.degree. C. cloud point reduction compared to the starting base
stock LN321. also the blend had higher VI than the base stock, i.e., 111
versus 106 for the base stock.
TABLE 2
______________________________________
Composition of Starting Olefin Mixtures and Polymers
Carbon Olefin Wt % Wt % after
Conversion
% Olefin in
Number MW in Mix. 24 hrs % Polymer
______________________________________
6 84 6.8 1.9 72 6
8 112 9.4 0.8 91 11
10 140 13.3 1.2 91 15
12 168 11.1 1.1 90 12
14 196 11.8 3.1 74 11
15 210 7.5 1.7 77 7
16 224 7.6 1.2 84 8
18 252 6.2 1.6 74 6
20 280 25.6 6.8 73 23
20+ 282 0.7 0.4 43 0
Polymer
-- 0 80 -- --
______________________________________
EXAMPLE 4
The same base stock used in Example 3 was blended with a commercial VI
improver, Acryloid 956 (Example 4A), or commercial pour point depressant
Acryloid 156 (Example 4C, and NALCO 5644 (Example 4B). The pour points of
the blends were decreased only 2.degree. to 26.degree. C. and the cloud
points remained the same as the base stock as shown in Table 3.
EXAMPLE 5
The product of Example 2 was blended with a mineral oil (LN142) which was
prepared using a conventional solvent dewaxing process. The properties of
the base stock and blends are summarized in Table 3. These data show that
the blend containing 0.49 weight percent of the product of Example 2 had a
pour point of -37.degree. C. and cloud point of -12.9.degree. C. This
corresponds to a 23.degree. C. pour point reduction and 3.5.degree. C.
cloud point reduction compared to the starting base stock. Also, the blend
has higher VI than the base stock, 109 versus 97 for the stock.
EXAMPLE 6
A blend was prepared as described in Example 3, except the base stock was a
heavy neutral mineral basestock HN339. The pour point of HN339 was
depressed from -12.degree. C. to -27.degree. when 0.26 weight percent of
the product of Example 2 was blended.
EXAMPLE 7
A blend was prepared as described in Example 3, except the base stock was
mineral bright stock BS345. The pour point of BS 345 was depressed from
+4.degree. C. to -12.degree. C. when 0.55 weight percent of the product of
Example 2 was added.
EXAMPLE 8
A blend was prepared as described in Example 3, except the base stock was
prepared from a wax hydroisomerization process. In this case, the pour
point was depressed from -15.degree. C. to -23.degree. C.
TABLE 3
__________________________________________________________________________
V@100.degree. C.,
Cloud
Example No.
Base oil Type
VII/PPD type
Wt % VII/PPD
Pour point, .degree.C.
V@40.degree. C.,
cS VI Point
__________________________________________________________________________
.degree.C.
No. 3 LN321 none 0 -3 24.1 4.61 106
5.6
" " Exam.2 0.26 -38 24.81 4.74 111
" " " 0.58 -28 25.87 4.94 116
1.5
No. 4 comparative
4A " Acryloid 956
0.25 - 5 24.47 4.71 111
6.2
4B " Nalco-5644
0.26 -26 24.15 4.63 107
na
4C " Acryloid 156
0.24 -29 24.38 4.71 112
na
No. 5 LN142 none 0 -14 21.32 4.19 97
" " Exam. 2 0.49 -37 22.28 4.43 109
-12.9
" " " 1.05 -32 23.94 4.71 115
-14.0
No. 6 HN339 none 0 -12 138.53 13.08 86
na
" " Exam. 2 0.26 -27 140.53 13.45 89
na
" " " 0.5 -29 143.35 13.68 90
na
No. 7 BS345 none 0 4 460.62 30.2 94
na
" " Exam. 2 0.55 -12 468.05 30.78 95
na
" " " 1.09 -14 486.05 32.91 100
na
No. 8 WHI-A none 0 -16 26.1 5.35 144
14.7
" " Exam. 2 0.65 -20 29.21 5.78 144
-14.2
" " " 1.31 -18 30.22 6.13 157
-14.8
No. 9 PAO-1 none 0 -66 5.2 1.7 90
na
" " Exam. 2 0.51 -78 5.47 1.82 106
na
" " " 1.73 -69 6.39 2.13 144
na
No. 10 PAO-2 none 0 -62 30.5 5.5 135
na
" " Exam. 2 0.45 -71 30.95 5.95 141
na
" " " 1 -64 32.68 6.22 142
na
__________________________________________________________________________
EXAMPLE 9
A blend was prepared as described in Example 3, except the base stock was a
low viscosity polyalphaolefin product of 1.7 cS. A 12.degree. C. pour
point reduction was observed.
EXAMPLE 10
A blend was prepared as described in Example 3, except the base stock was a
synthetic PAO base stock of 5.6 cS (stock 509). The pour point reduction
was 9.degree. C.
EXAMPLE 11
A series of blends was prepared using a Coryton diesel fuel having a pour
point of -13.3.degree. C. and a cloud point of -2.9.degree. C. and the
HVI-PAO product of Example 2. Pour points and cloud points were measured
on the blends of these mixed HVI-PAO oligomers with the diesel fuel and
the results are presented in Table 4. It was found that the mixed HVI-PAO
is at least comparable to commercial fuel pour point depressants. However,
the mixed HVI-PAO had extra cloud point depression which is not observed
with the commercial pour point depressants.
TABLE 4
______________________________________
HVI-PAO Pour Point Cloud Point
ppm .degree.C. .degree.C. .DELTA.PP
.DELTA.CP
______________________________________
100 -31 -6.3 17.7 3.4
200 -26.5 -5.8 13.2 2.9
500 -28.7 -6.8 15.4 3.9
______________________________________
EXAMPLE 12
A two component HVI-PAO was prepared according to the general procedure
described in Example 2. The components were 1-decene and 1-octadecene.
Oligomers were prepared from feeds containing 7% 1-octadecene, 25%
1-octadecene and 40% 1-octadecene. When blends were prepared of mineral
oil (LN321) containing the HVI-PAO oligomers, the corresponding pour point
depression was -30.degree. C. for 40% 1-octadecene, -13.degree. C. for 25%
1-octadecene and -7.degree. C. for 7% 1-octadecene.
The amount of pour point depression depends on the concentration of mixed
HVI-PAO in the blend. The optimum concentration for the largest pour point
depression is about 0.1 weight percent to about 0.4 weight percent.
Usually the best results are achieved using 0.20-0.30 weight percent,
preferably 0.25 weight percent. Above or below this concentration the
amount of depression decreases. However, even at low concentrations in the
range of 50-100 ppm a 5.degree.-12.degree. C. pour point depression is
observed.
The HVI-PAO oligomers effective as pour point depressants in the present
invention comprise copolymers of C.sub.3 -C.sub.28 1-alkenes. The
copolymer contains at least 10 weight percent of C.sub.14 -C.sub.24
1-alkenes; has a number average molecular weight between 5,000 and 60,000;
a molecular weight distribution between 1 and 10.
An important part of the novelty of the present invention resides in the
discovery that the copolymerization of certain mixtures of .alpha.-olefins
according to the process of the invention leads to oligomers of unique
structure (MHVI-PAO) with unexpectedly superior properties as pour point
depressants and, even more notable, combined pour point depressants and
viscosity index improves. The novel oligomers are produced from mixed
.alpha.-olefin feedstock having a bimodal distribution of carbon numbers
for the .alpha.-olefins. The distribution is such that the carbon numbers
reach one maximum at a relatively high carbon number and another or second
maximum at a relatively low carbon number. The preferred oligomers of the
invention are characterized by exhibiting both maxima. This bimodal
feedstream leads to the formation of oligomers of the present invention
comprising copolymers having a first maximum of pendant carbon chains with
between one and twelve carbon atoms and a second maximum of pendant carbon
chains with between twelve and twenty-four carbon atoms. In terms of
1-alkene content, the oligomer or coploymer residue contains recuring
units comprising a bimodal distribution of 1-alkenes having a first
maximum between C.sub.3 and C.sub.14 1-alkenes and a second maximum
between C.sub.14 and C.sub.26 1-alkenes.
Referring to FIG. 1, a graphical representation is presented comparing the
feed composition of HVI-PAO versus the novel MHVI-PAO oligomers of the
invention. The graph shows that the prior art HVI-PAO oligomers employ
monomodal feed mixtures having a single maximum of relatively low
.alpha.-olefin carbon number. Feeds for other MHVI-PAO oligomers of the
invention are also presented as bimodal. The distinction is emphasized by
referring to FIG. 2 which shows the monomodal feed composition used for
prior art HVI-PAO synthesis. FIGS. 3-5 illustrate MHVI-PAO feed
compositions for particularly preferred oligomers of the invention
prepared from two or more .alpha.-olefins. Regardless of the mix, FIGS.
3-5 show the uniquely bimodal distribution of olefins in the MHVI-PAO
feedstream with one maximum of six to ten carbon atoms and a second
maximum falling between sixteen and twenty carbon atoms. Notably, the
required bimodal character of the feed does not preclude a continuum in
.alpha.-olefin carbon numbers in the feed. This is illustrated in FIG. 4.
As noted herein before, liquid hydrocarbon polymers and copolymers of alpha
olefins (HVI-PAO) have been prepared by reduced chromium oxide
oligomerization as disclosed particularly in U.S. Pat. No. 4,827,064 to M.
Wu. These lubricant range oligomers exhibit unexpectedly high viscosity
indices and low pour points. While these polymers are compositionally
different than the polymers of the present invention, their similarity is
sufficient to provide a basis to conjecture that the (HVI-PAO)
compositions of U.S. Pat. No. 4,827,064 would also be effective pour
points depressants. Accordingly, a series of experiments were carried out
(Examples 13-16) to compare the pour point depressant properties of the
HVI-PAO compositions of U.S. Pat. No. 4,827,064 with the products of the
instant invention.
In Examples 13-16, using 1-decene or C.sub.6 -C.sub.14 alpha olefins,
HVI-PAO oligomers were prepared according to the above cited patent and
the polymer or copolymer product blended with Stock 142 mineral oil. The
results of these experiments are presented in Table 5. The results show
that the HVI-PAO containing no C.sub.16 or higher .alpha.-olefins produced
no pour point depressant effect with Stock 142 mineral oil. Consequently,
the products of the present invention are distinguished over those of
other HVI-PAO patents such as U.S. Pat. No. 4,827,064.
TABLE 5
______________________________________
Blend Properties
Ex- V@100.degree. C.
V@40.degree. C.
Pour
ample HVI-PAO cS cS VI Point .degree.C.
______________________________________
LN142 mineral oil
4.03 20.02 97 -14
Exam. 3300 cS 1- 4.15 20.49 103 -16
13 decene
HVI-PAO
Exam. C.sub.6 -C.sub.14 -16
14 .alpha.-olefins
Exam. 1-decene & -15
15 4-methyl-1-
pentene
Exam. 57 cS 4.06 20.09 100 -14.degree. C.
16 HVI-PAO
from 70/30
C.sub.10 /C.sub.20-24
______________________________________
A key discovery of the present invention is the fact that the products of
the invention, in order to demonstrate a large pour point depressant
effect must contain a relatively high proportion of higher carbon number
alpha olefins. Optimally, the feed to the oligomerization process should
contain a relatively higher proportion of alpha olefins having a carbon
number of C.sub.16 -C.sub.20. In this case, the addition of a small
quantity of the copolymer of the invention to a lubricant base stock will
provide a significant reduction in pour point. Surprisingly, the additive
of the invention, besides contributing pour point lowering of the
lubricant fluid, also act as a viscosity index improver (VII) and
increases the viscosity index of the lubricant. This effect is achieved
simultaneously, i.e., pore point is depressed while viscosity index of the
lubricant is increased. Therefore, the products of the invention act as an
additive which both reduces a lubricant base stock pour point (PPD) and
increases viscosity index (VII).
The following examples 17-22 are presented to illustrate the qualities of
the product of the invention to lower pour point and to increase viscosity
index. Examples 17-20 are presented to specifically illustrate the effect
of various copolymer compositions containing a relatively high proportion
of higher carbon number alpha olefins in the feed. Examples 21-22 present
the results of experiments showing the ability of the products of the
invention to simultaneously reduce pore point and increase viscosity
index.
EXAMPLE 17
A copolymer of Mn (number average molecular weight) 8.845 and MWD
(molecular weight distribution) 3.34 was prepared by reacting an
.alpha.-olefin mixture containing 1-hexene, 1-hexadecene, 1-octadecene and
1-eicosene (46 wt %, 20 wt % and 20%, respectively) over an activated
Cr/SiO.sub.2 catalyst. When 0.20 wt % of this polymer was blended with
LN142 lubricant base stock, the pour point of the base oil was depressed
from -14.degree. C. down to -38.degree. C. This example demonstrated that
C.sub.16 -C.sub.20 .alpha.-olefins are necessary components for good PPD
effect.
EXAMPLE 18
A copolymer was prepared as described in Example 17, except the starting
olefins contain 1-hexene and 1-octadecene (50 wt % and 50%, respectively).
When 0.27 wt % of this polymer, with Mn 11,890 and MWD 5.8, was blended
with LN142, the pour point was depressed from -14.degree. C. down to
-36.degree. C.
EXAMPLE 19
A copolymer was prepared by the process of the invention with Mn of 28,630
and MWD of 3.97 from an alpha-olefin mixture containing 70% 1-decene and
30% Gulftene C.sub.20-24 .alpha.-olefins. When 0.24% of this polymer was
blended with LN142 base stock, the pour point decreased from -14.degree.
C. to -36.degree. C.
EXAMPLE 20
A copolymer with Mn 35,220 and MWD 4.32 was prepared from an alpha-olefin
mixture containing 50% 1-decene, 25% C.sub.20-24 .alpha.-olefins (Gulftene
20-24) and 25% C.sub.24-28 .alpha.-olefins (Gulftene 24-28). When 0.22% of
this polymer was blended with LN142 base stock the pour point was
depressed to -22.degree. C. from -14.degree. C.
EXAMPLE 21
A mixed HVI-PAO copolymer of the invention was prepared from a mixture
containing 60% 1-decene and 40% 1-octadecene to provide a copolymer having
a number averaged MW of 30,100 and MWD (molecular weight distribution) of
9.02. The copolymer so formed was blended with a 150 sus mineral oil, LN
321. and demonstrates that the mixed HVI-PAO copolymer can function as
both a VI improver and a pour point depressant when higher concentrations
of the mixed HVI-PAO copolymer are blended with a mineral oil basestock.
The results are summarized in the following Table 6. The results show that
when up to 1 weight % mixed HVI-PAO copolymer of the invention was blended
with the mineral oil both the VI and the pour point improved
significantly.
EXAMPLE 22
An experiment was carried out similar to Example 21 except the mixed
HVI-PAO copolymer was prepared from a mixture of 50% C6 and 50% C18
.alpha.-olefins and had a Mn of 11.900 and MWD of 5.8. The base oil used
in Example 22 is a 100" mineral oil stock 142. The results are presented
in Table 7. As in the previous Example 21, this example demonstrates that
the mixed HVI-PAO copolymer of the invention improves the pour point and
VI of the base stock simultaneously.
TABLE 6
______________________________________
Mixed HVI-PAO and Stock LN321 (Example 21)
Wt % V@100.degree. C. .degree.C.
HVI-PAO cS VI Pour Point
.DELTA.VI
.DELTA.pour point
______________________________________
0 4.61 106 -3 -- --
0.25 5.19 114 -30 8 27
0.48 5.19 118 -37 15 34
1.18 5.98 133 -39 27 36
______________________________________
TABLE 7
______________________________________
Mixed HVI-PAO and LN142 (Example 22)
Wt % V@100.degree. C. .degree.C.
HVI-PAO cS VI Pour Point
.DELTA.VI
.DELTA.pour point
______________________________________
0 4.03 97 -14 -- --
0.27 4.18 97 -36 0 22
0.67 4.46 111 -38 14 24
1.08 4.74 121 -38 24 24
______________________________________
Specifically preferred mixtures of 1-alkene monomers useful as feedstream
for the present invention include: C.sub.6, C.sub.8, C.sub.10, C.sub.12,
C.sub.14, C.sub.15, C.sub.16, C.sub.18 and C.sub.20 1-alkenes; C.sub.6 and
C.sub.18 1-alkenes; C.sub.10 and C.sub.20-24 1-alkenes; C.sub.10 and
C.sub.20-28 1-alkenes; C.sub.6, C.sub.16, C.sub.18 and C.sub.20 1-alkenes,
and C.sub.10 and C.sub.18 1-alkenes.
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